Investigations regarding mixing and dispersing nanofibers with a metal, polymer or ceramic matrix have been progressing for several years. In particular, C. L. Xu, B. Q. Wei, R. Z. Ma, J. Liang, X. K. Ma, D. H. Wu in “Carbon,” Vol. 37, 1999, pp 855-858, and J. W. Ning, J. J Zhang, Y. B. Pan and J. K. Guo in “Materials Science and Engineering,” Vol. A313, 2001, pp 83-87, describe a method of manufacturing and evaluating a composite such as carbon nanotube-reinforced aluminum matrix via powder mixing and sintering.
However, in this conventional method, carbon nanotubes are not uniformly dispersed in the aluminum matrix and aggregate at grain boundaries, causing deterioration in sintering capability when producing the composite, and deterioration in mechanical and electrical properties of the composite, which leads to a failure of achieving remarkably enhanced properties. In other words, when the composite is formed, the carbon nanotubes agglomerate on the surface of the powdered metal matrix due to insufficient dispersion of the carbon nanotubes, so that the surface of the metal matrix having agglomeration of the carbon nanotubes acts as a defect, thereby deteriorating the mechanical properties of the matrix while making it difficult to achieve enhanced mechanical properties by addition of the carbon nanotubes.
In addition, Haihui Ye, Hoa Lam, Nick Titchenal, Yury Gogotsi and Frank Ko in “Applied Physics Letters,” Vol. 85, No. 10, 2004, pp 1775-1777, and Kunihiko Nishimura, Zhiying Shen, Masahiro Fujikawa, Akihiko Hosono, Noritsuna Hashimoto, Satoru Kawamoto, Shoyu Watanabe, Shuhei Nakata in “Technical Digest of IVMC2003,” Vol. O5-4, pp 49-50, describe that a polymer matrix is enhanced in mechanical properties as a composite of the polymer matrix with carbon nanotubes, and is widened in applications, for example, field emission displays (FED), by using the electrical properties of the carbon nanotubes.
However, since such a conventional method of dispersing the carbon nanotubes comprises complicated processes such as dispersion in a dispersive solvent, sintering, etc., there is a need of a method for uniform dispersion of the carbon nanotubes through a simple process in order to enhance manufacturing efficiency.
There is a method which uniformly disperses nanofibers in a metal, polymer or ceramic matrix via various processes, such as ultrasonic treatment, mixing of metallic salts, ultrasonic treatment, drying, calcination, reduction, and the like after dispersing the nanofibers in the metal, polymer or ceramic matrix via a suitable dispersive solvent. However, this method requires controlling of various process factors such as kinds of dispersive solvent, amount of solvent according to a fraction, calcination temperature, reduction conditions, etc., and must be performed for several processes requiring a great deal of time. Thus, this method has problems in that it is difficult to manufacture a reproducible composite, and in that industrial efficiency is reduced.
Meanwhile, although various methods for enhancing the directionality of the carbon nanotubes have been investigated in order to enhance the mechanical and electrical properties, there is still a need of a method which solves the problem of complicated processing conditions.